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The frog inner ear: picture perfect?

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Mason, Matthew J 
Segenhout, Johannes M 
Cobo-Cuan, Ariadna 
Quiñones, Patricia M 
van Dijk, Pim 


Many recent accounts of the frog peripheral auditory system have reproduced Wever's (1973) schematic cross-section of the ear of a leopard frog. We sought to investigate to what extent this diagram is an accurate and representative depiction of the anuran inner ear, using three-dimensional reconstructions made from serial sections of Rana pipiens, Eleutherodactylus limbatus and Xenopus laevis. In Rana, three discrete contact membranes were found to separate the posterior otic (=endolymphatic) labyrinth from the periotic (=perilymphatic) system: those of the amphibian and basilar recesses and the contact membrane of the saccule. The amphibian 'tegmentum vasculosum' was distinguishable as a thickened epithelial lining within a posterior recess of the superior saccular chamber. These features were also identified in Eleutherodactylus, but in this tiny frog the relative proportions of the semicircular canals and saccule resemble those of ranid tadpoles. There appeared to be a complete fluid pathway between the right and left periotic labyrinths in this species, crossing the cranial cavity. Xenopus lacks a tegmentum vasculosum and a contact membrane of the saccule; the Xenopus ear is further distinguished by a lateral passage separating stapes from periotic cistern and a more direct connection between periotic cistern and basilar recess. The basilar and lagenar recesses are conjoined in this species. Wever's diagram of the inner ear of Rana retains its value for diagrammatic purposes, but it is not anatomically accurate or representative of all frogs. Although Wever identified the contact membrane of the saccule, most recent studies of frog inner ear anatomy have overlooked both this and the amphibian tegmentum vasculosum. These structures deserve further attention.


This is the accepted manuscript of a paper published in the Journal of the Association for Research in Otolaryngology (2015) DOI: 10.1007/s10162-015-0506-z


Animals, Anura, Ear, Inner, Image Processing, Computer-Assisted, Rana pipiens, Xenopus laevis

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J Assoc Res Otolaryngol

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Springer Science and Business Media LLC
The authors wish to thank Emanuel Mora for his help and support with this project. Dave Simpson kindly provided the Xenopus specimens. The CT scan of Xenopus was made by Alan Heaver of the University of Cambridge Department of Engineering, with thanks going also to Norman Fleck for the use of his equipment. The authors are very grateful to Dolores Bozovic, Alan D. Grinnell, Tammy Hoang, Victoria Sandoval and Felix E. Schweizer for facilitating the Rana CT scan, which was made by Ting-Ling Chang at the UCLA School of Dentistry, Division of Advanced Prosthodontics. Stephan Kamrad helped with translations. The research of JMS and PvD was supported by the Heinsius Houbolt Foundation and is part of the research programme Healthy Ageing and Communication of the Department of Otorhinolaryngology at the University Medical Center Groningen. Finally, the authors wish to thank the reviewers and editors of the manuscript for their very helpful comments.